In record amplifiers, it is desirable to have a closed feedback system involving the magnetic recording head so that any change in the head parameters are automatically compensated for by negative feedback. One problem with a negative feedback circuit, however, is that all such circuits have a finite amount of time delay for signals passing through the amplifier. Provided that this circuit delay is small compared to the period of the signal, this does not present a problem. However, as the frequency of the signal increases, that is at higher bandwidths, the circuit delay begins to approach one half of the period of the signal which is the equivalent of 180.degree. of phase shift. Thus the output signal from the amplifier is inverted with respect to the input signal. When a portion of this phase shifted output signal is negatively fed back, it amounts to positive feedback and causes oscillation.
The problem with prior art record amplifiers has been that an adequate amount of signal amplification was not achievable without so much circuit delay that the bandwidth of the amplifier was severely limited by the foregoing principle. The best way, of course, to reduce the amount of signal delay is to have the minimum number of amplifying components in the circuit, but without sacrificing overall signal gain. The present invention achieves high gain with a minimum number of circuit components to thereby reduce the circuit signal delay and thus increase the bandwidth.